The present invention is directed to linkages for controlling switches and more particularly to a linkage for use as a double throw switch for controlling two switches mounted in the same enclosure so that only one switch can be on at any given time.
It is of paramount importance that emergency generators be insulated from the incoming electric transmission source when the incoming power source is dead. These generators are commonly found in the home, and are often connected to a 30 amp device such as an electric dryer. If the breaker connecting the external electric transmission, i.e. the power company, be in an “on” position at the same time as the emergency generator delivers power to the home, an extremely dangerous situation exists. Under this condition, even though the utility power line is disconnected from the external power source, i.e. the utility company, the emergency generator nonetheless places a dangerous voltage on the power line. Serious injuries and death from electrocution have occurred as a result of a homeowner's emergency generator transmitting power from the home through the power line, for example when a utility operator was working on the transmission line following storm damage. Accidents occur when the utility worker believes the transmission line is dead from the utility source, and shows no voltage, but the homeowner un-expectantly activates the generator.
Switching apparatus generally referred to as a double throw switch is commonly used to alternately connect one of two load devices to a source of electric power or to connect a single load device alternately to one of two separate sources of electric power. One example would be two lines coming into a switch tied to one load coming out of the switch as in a system that has an emergency power generator to switch from normal power source to the emergency generator. Another example is one line coming into a switch tied to two loads coming out of the switch as in a system that has a backup pump that needs to operate when the main pump is off line. The two switch mechanisms are tied together with a linkage. The linkage allows only one switch to be turned on at any given time. Prior linkages typically are assembled using multiple slots in a plate which is secured to a framework by multiple fasteners or rivets which slide in the plurality of slots.
There is a need for a double throw switch linkage that requires fewer parts for assembly thereby reducing costs and complexity.
U.S. Pat. No. 6,815,623, issued to Holland, discloses a double throw switch linkage for coupling two switch apparatuses together in an enclosure. Each switch apparatus is coupled to the switch mechanism having a switch mechanism lever arm. The double throw switch linkage comprises an interlock housing, with the interlock housing defining a pair of actuator plate slots and a first orifice and a second orifice. Each orifice is configured to provide unimpeded passage of each switch mechanism lever arm. An actuator plate is slidingly mounted in the actuator plate slots. The actuator plate is free floating in the interlock housing. The actuator plate defines a first switch slot, a second switch slot, and a driver arm slot. Each switch slot is configured to guide a pin mounted on each switch mechanism lever arm. A lever arm assembly is mounted on a sidewall of the enclosure with the lever arm assembly including a lever arm coupled to a driver arm. The driver arm is configured to engage the driver arm slot and the actuator plate. When the lever arm is moved it translates a force to the actuator plate which closes one switch mechanism and maintains the other switch mechanism in an open position.
U.S. Pat. No. 6,872,900 to Lament et al. discloses a double throw switch linkage for coupling two switch apparatuses together in an enclosure. Each switch apparatus is coupled to the switch mechanism having a switch mechanism lever arm. When the lever arm is moved it translates a force to the actuator plate which closes one switch mechanism and maintains the other switch mechanism in an open position.
U.S. Pat. No. 8,022,319 issued to Lament et al. discloses a switch that comprises a handle operator linkage for a double throw switching apparatus. A handle operator linkage has a lever arm connected to a mid-section, and wherein a stem section connects a base to the mid-section with a pivot hole and at least one first bump facing the base section. The base section has a back bump, which faces the at least one first bump, and thereby forming the handle operator linkage for a double throw switching apparatus.
None of these prior solutions provides a simple, reliable and cost effective double-throw switch. One problem inherent with the above double throw toggles is that the cover for the normal breaker box cannot be closed.